Severity of emphysema predicts mortality
Severity of emphysema, as measured by computed tomography (CT), is a strong independent predictor of all-cause, cardiovascular, and respiratory mortality in ever-smokers with or without chronic obstructive pulmonary disease (COPD), according to a study from researchers in Norway. In patients with severe emphysema, airway wall thickness is also associated with mortality from respiratory causes.
“Ours is the first study to examine the relationship between degree of emphysema and mortality in a community-based sample and between airway wall thickness and mortality,” said lead author Ane Johannessen, PhD, post-doctoral researcher at Haukeland University Hospital in Bergen, Norway. “Given the wide use of chest CT scans around the world, the predictive value of these measures on mortality risk is of substantial clinical importance.”
The findings were published online ahead of print publication in the American Thoracic Society’s American Journal of Respiratory and Critical Care Medicine.
The study included a community-based cohort of 947 ever-smokers with and without COPD who were followed for eight years. All subjects underwent spirometry and CT scanning. Degree of emphysema was categorized as low, medium, or high based on the percent of low attenuation areas (areas with lower density than normal) on CT. COPD was diagnosed by spirometric measurement of airway obstruction. Of the 947 patients, 462 had COPD.
During follow-up, four percent of the 568 subjects with a low degree of emphysema died, compared with 18 percent of the 190 patients with a medium degree of emphysema and 44 percent of the 189 patients with a high degree of emphysema.
After adjustment for sex, COPD status, age, body mass index, smoking and measures of lung function, survival in the low emphysema group was 19 months longer than survival in the middle and high emphysema groups for all-cause mortality. Compared with subjects in the low emphysema group, subjects with a high degree of emphysema had 33 months shorter survival for respiratory mortality and 37 months shorter survival for cardiovascular mortality.
Stages of Emphysema
Emphysema is separated into four stages: at-risk, mild emphysema, moderate emphysema, and severe emphysema. In order to determine if someone has emphysema and which stage he or she is in, the doctor will use a breathing test called spirometry. Spirometry is the most sensitive and commonly used test of lung functions—it is able to detect emphysema long before a person has significant symptoms.
Determining the Stages of Emphysema
In order to determine if someone has emphysema and the stage of emphysema, your doctor will use a breathing test called spirometry. This test is easy and painless and shows how well your lungs work. You breathe hard into a large hose connected to a machine called a spirometer. When you breathe out, the spirometer measures how much air your lungs can hold and how fast you can blow air out of your lungs after taking a deep breath.
Spirometry is the most sensitive and commonly used test of lung functions. It can detect emphysema long before you have significant symptoms.
Emphysema was a significant predictor of all cause-specific mortalities, with increasing emphysema levels predicting shorter survival. While airway wall thickness was not an independent predictor of mortality, increased airway wall thickness reduced survival time in patients with more severe emphysema.
The GOLD Emphysema Staging System
One major emphysema staging system is called GOLD. It was created by an expert group called the Global Initiative for Chronic Obstructive Lung Disease.
The major factor in GOLD emphysema staging is the amount of air a person with emphysema can forcefully exhale in one second. This is called the forced expiratory volume, or FEV1.
GOLD emphysema staging is as follows:
Stage I, Mild emphysema: FEV1 greater than or equal to 80% of normal
Stage II, Moderate emphysema: FEV1 less than 80%, but greater than or equal to 50% of normal
Stage III, Severe emphysema: FEV1 less than 50%, but greater than or equal to 30% of normal
Stage IV, Very severe emphysema: FEV1 less than 30% of normal, OR less than 50% of normal with low blood oxygen levels
GOLD emphysema staging is well established and widely used. However, GOLD emphysema staging does not include other areas of functioning that are important, such as how people living with emphysema feel.
“The relationship between emphysema levels and mortality we found can be used in the risk assessment of these patients,” concluded Dr. Johannessen. “Accurately predicting mortality risk may help target patients for specific therapeutic interventions which may improve outcomes.”
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About the American Journal of Respiratory and Critical Care Medicine:
With an impact factor of 11.080, the AJRRCM is a peer-reviewed journal published by the American Thoracic Society. It aims to publish the most innovative science and the highest quality reviews, practice guidelines and statements in the pulmonary, critical care and sleep-related fields.
Founded in 1905, the American Thoracic Society is the world’s leading medical association dedicated to advancing pulmonary, critical care and sleep medicine. The Society’s 15,000 members prevent and fight respiratory disease around the globe through research, education, patient care and advocacy.
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Nathaniel Dunford
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American Thoracic Society